@inproceedings{schroeder1972a,
author = {Schroeder, Mike and Saltzer, Jerome H.},
title = {A hardware architecture for implementing protection rings},
booktitle = {Communications of the ACM & Proceedings of the 3rd ACM Symposium on Operating Systems Principles},
year = {1972},
month = {March},
abstract = {Protection of computations and information is an important aspect of a computer utility. In a system which uses segmentation as a memory addressing scheme, protection can be achieved in part by associating concentric rings of decreasing access privilege with a computation. This paper describes hardware processor mechanisms for implementing these rings of protection. The mechanisms allow cross-ring calls and subsequent returns to occur without trapping to the supervisor. Automatic hardware validation of references across ring boundaries is also performed. Thus, a call by a user procedure to a protected subsystem (including the the supervisor) is identical to a call to a companion user procedure. The mechanisms of passing and referencing arguments are the same in both cases as well.},
publisher = {Association for Computing Machinery, Inc.},
url = {http://approjects.co.za/?big=en-us/research/publication/a-hardware-architecture-for-implementing-protection-rings/},
edition = {Communications of the ACM & Proceedings of the 3rd ACM Symposium on Operating Systems Principles},
}